By Anne Harding

NEW YORK (Reuters Health) - People with shorter arms and legs may be more likely to develop Alzheimer's disease, and poor nutrition in early life is the probable culprit, according to new research published in Neurology.

Arm span and knee height are indicators for how well nourished a person was in early childhood, Dr. Tina L. Huang of Tufts University in Boston, who was involved in the study, told Reuters Health. "All those factors that are involved with making a healthy baby are maybe also important in dementia and Alzheimer's disease risk," she said in an interview.

Huang and her team decided to investigate the relationship between limb length and dementia risk because the portion of the brain that bears the brunt of Alzheimer's disease develops just as the limbs are growing most rapidly. They looked at 2,798 men and women participating in the Cardiovascular Health Cognition Study who were followed for about five years, during which time 480 developed dementia.

Among women, the researchers found, dementia and Alzheimer's disease risk decreased as knee height and arm span increased.

Women with the shortest arm spans were 50 percent more likely to have developed dementia than those with the longest arm span, while dementia and Alzheimer's disease risk fell by 16 percent for every additional inch of leg length.

For men, knee height wasn't related to dementia or Alzheimer's risk, but dementia risk fell by 6 percent for every additional inch in arm span.

Both genetics and environment influence limb length, the researchers note in their report, although the role of environment is generally greater in developing nations.

Studies in elderly South Korean people linked shorter arms and legs to greater dementia risk, Huang noted, adding that it was "surprising" to find the association in an American population, for whom getting enough to eat was probably not a major problem.

Based on the current study, she added, "We have to think about the quality of nutrition as well as making sure that people get enough food."

SOURCE: Neurology, May 6, 2008.

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